Allylic oxidation is a fundamental organic reaction of significant interest to organic chemists practicing in a variety of fields ranging from agricultural products to pharmaceuticals. A variety of procedures are known for allylically oxidizing various organic compounds. Unfortunately, such procedures typically suffer from unsatisfactory yields, tedious workups and/or require the use of expensive and/or ecologically and physiologically undesirable reagents.
Allylic oxidation reactions have traditionally been performed with chromium reagents, such as a CrO.sub.3 -pyridine complex, a mixture of chromium trioxide and 3,5-dimethylprazole, pyridinium chlorochromate (PCC), pyridinium dichromate (PDC), sodium chromate, or sodium dichromate in acetic acid. However, the great excess of reagent and the large volume of solvent required in such procedures, in combination with the difficult work-up required of the environmentally hazardous chromium residues, causes such procedures to be inconvenient for large scale production.
Of greater preparative interest has been the use of hydroperoxides with various catalysts to effect allylic oxidation. For example, the use of Cro.sub.3 as a catalyst in the allylic oxidation of .DELTA.5 steroids yields .DELTA.5-7-ketones as the allylic oxidation product, along with minor quantities of a reaction product in which the double-bond is epoxidized. While good yields have been reported with hexacarbonyl chromium, Cr(CO).sub.6 pyridinium dichromate and RuCl.sub.3 in the preparation of allylic oxidation products from .DELTA.5-steroids, the toxicity of the chromium reagents and the high cost of the ruthenium catalyst renders commercialization of the procedures inconvenient.
Hence, a continuing need exists for a simple, efficient, safe and cost effective procedure for selectively effecting the allylic oxidation of organic compounds, particularly .DELTA.5-steroids.